1. Field of the Invention
The present invention relates to an electro-hydraulic control means for controlling a continuously variable loop transmission and, more particularly, to an electro-hydraulic control means for controlling a hydraulic pressure in a continuously variable loop transmission including a hydraulic bevel disk axial displacement device provided with a secondary piston chamber and a pump for supplying the secondary piston chamber with hydraulic oil in order to provide a clamping force in the displacement device, wherein the control means includes several individual valves for adjusting the hydraulic pressure including a proportioning pressure relief valve and a flow control valve. The invention also relates to a loop transmission including the aforementioned control means.
2. Prior Art
A hydraulic control for an electronically controlled continuously variable transmission (continuously variable transmission: CVT) is described in EP 0 451 887 A1. The CVT transmission, which is preferably used in automobiles has, among other things, an electronic control which regulates the hydraulic oil pressure in the secondary side of the piston chamber in order to set the clamping force during normal driving operations in such a way that advantageous transmission effectiveness is achieved. For regulating the secondary oil pressure, the control requires the vicinity actual pressure value in the area of the secondary side piston chamber. A pressure sensor is disposed there for this purpose. The nominal pressure is adjusted as a function of the measured actual pressure via a directly controlled valve.